Hi, guys! I just noticed BusyBox can also provide a DHCPv6 client. I don't know if it has enough features to replace odhcp6c, but it would be nice if it were supported by OpenWrt, even if just for testing purposes (although I'm personally still stuck with IPv4, thanks to my shitty ISP). Is such a thing within the realms of possibility? Thanks in advance. 
You likely can build your own image from source, enabling that applet, and re-examine the reasons why udhcpc6 was selected.
I always do my own builds, but there's (to the best of my knowledge) no DHCP script to support udhcpc6, which is why I asked the question in the first place.
You’ll perhaps also find ubus support lacking in the busybox version, so poor/no integration with interface management or other services when the IA_NA or IA_PD state changes.
Oh, right, I hadn't thought of that. Indeed, I see some udhcpc patches for BusyBox, but nothing related to netifd and/or ubus…